In theory, the European Union’s parliamentary elections are the most international in the world. The winners serve in a multinational legislature. They speak to one another with the help of hundreds of translators. They are members of transnational parties: In the parliament buildings in Brussels and Strasbourg, center-left MEPs from across Europe sit with the Party of European Socialists, center-right MEPs caucus with the European People’s Party, and so on.

Nevertheless, European elections have never quite fulfilled this multinational promise. Usually they consist of dozens of campaigns, each dominated by national debates. In most years, the German Christian Democrats don’t go on the hustings on behalf of their Swedish counterparts, and the Portuguese input into the Slovakian elections is pretty negligible. But this year is different. This year, the European elections set for late May have continent-wide themes and a continent-wide significance. Ironically, or perhaps absurdly, that is because this year, the anti-Europeans — the politicians who want to sweep the institutions away altogether — are making a public attempt to work together, across national lines, to achieve common goals.

Strange though it sounds, this phenomenon, the Nationalist International (or perhaps the “Populist International”) is not new. The online activists, trolls and bots of the far right and the alt-right have long cooperated in cyberspace. In advance of last year’s German elections, I was part of a research team that found the international alt-right sharing stories concocted by Russian state media and retweeting racist memes in support of the Alternative for Germany (AfD), Germany’s anti-European party. We found a similar nexus of online activists — Russian, American, German, French, even Polish — working together to denigrate the Swedish political system during their elections too.

Now some of that long-standing, semi-covert online coordination is openly moving offline. Last week, Matteo Salvini, the xenophobic, nationalist Italian deputy prime minister, traveled to Warsaw to meet with the leaders of Law and Justice, Poland’s xenophobic, nationalist ruling party. Salvini declared the opening of a “Polish-Italian axis”; their meeting was also hailed by Viktor Orban, the Hungarian leader who famously rails against nonexistent immigrants (there are very few in Hungary) whenever he is under pressure for corruption or abuse of power. Salvini has also held news conferences with Marine Le Pen, the French far-right leader, as well as Heinz Christian Strache, his Austrian counterpart. At each one, Salvini promises big changes, a new party, a pushback against immigration and against “Brussels.”

He has met with Stephen K. Bannon too, though Bannon’s own attempts to create a European alt-right movement (helpfully called “the Movement”) have stalled. Alas, its planned activities appear to be illegal in most European countries; more to the point, its platform is pretty vague. One of Bannon’s Italy-based collaborators did show up in Warsaw in December under the banner of a militant Catholic organization. He made a notably dull speech that attracted almost no attention at all.

This failure points to a deeper problem for Europe’s nationalist right. They can agree that they are “against” things, such as immigration. But what are they for? Destruction is easy; building is hard. More important, the number of immigrants is actually plunging, and alternative sources of self-righteous anger aren’t universally shared. Italian and Austrian nationalists have already clashed in South Tyrol, a partly German-speaking province of Italy, for example; French nationalists want Eastern Europeans to go home. Most of the far right in Europe, from Le Pen to Salvini to Orban, are enthusiastically pro-Russian; their Polish counterparts, with a few notable exceptions, are not.

But we’ve seen this movie before, and we know how it ends. After all, the precursor of this movement — its godfather, one might say — was Nigel Farage, the anti-European nihilist who led Britain into Brexit. He, too, had no positive agenda; he, too, used his E.U. parliamentary salary to torpedo the institution. The result was the worst constitutional and political crisis in Britain in many decades, and political polarization that may not end in our lifetimes.

The same fate awaits the rest of Europe if the rest of the political spectrum fails to unify, fails to set the agenda and fails to sell the benefits of the union — political, economic, environmental, even civilizational — to a new generation. Whatever happens, this will be the most interesting European election campaign there has ever been, not least because this time around there is so much to lose.

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Anne ApplebaumAnne Applebaum is a Washington Post columnist, covering national politics and foreign policy, with a special focus on Europe and Russia. She is also a Pulitzer Prize-winning historian and a professor of practice at the London School of Economics. She is a former member of The Washington Post's editorial board. Follow